A network system using existing virtualization technology virtually divides hardware resources to create slices, which are virtual networks that are logically constructed on a network infrastructure, with use of the virtualization technology disclosed in Non Patent Literature 1. The system then allocates a service to each of the slices and thereby provides the service using a network in each of the slices that are isolated from one another. Thus, when allocating a slice to each of services having a variety of requirements, it is possible to easily satisfy the requirement of each service and thereby reduce the signaling loads and the like.